Solving equations in Matlab

2013 4 29
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I am trying to solve a transcendental equation in Matlab, as follows:
fAc=solve((QAc-1)/(QAc+1)==f*arccosh(exp(0.693/f)/2),f);
I am getting the error:
Undefined function or variable 'f'.
Error in analyz (line 74)
fAc=solve((QAc-1)/(QAc+1)==f*arccosh(exp(0.693/f)/2),f);
and I'm not sure how to fix it. I have given QAc fake values that are approximately what they will really be.
Adding a "syms fAc" gives the error:
Undefined function 'arccosh' for input arguments of type 'sym'.
If I try to solve it in Mathematica, I get a complex number (and I want to eventually take the absolute value of it if it ends up being complex).
I know that Mathematica solves this a lot easier, but I'm not sure how to use the "ToMatlab.m" package that I've seen people refer to.
Any help is appreciated.
Thanks.

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Azzi Abdelmalek
Azzi Abdelmalek 2013-4-29

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It's not arccosh, It's acosh

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Grant
Grant 2013-4-29
I was using this as reference. I am using 2012a. Also, I get the same error if I change it to acosh.
Azzi Abdelmalek
Azzi Abdelmalek 2013-4-29
syms QAc f
fAc=solve((QAc-1)/(QAc+1)==f*acosh(exp(0.693/f)/2),f);
Grant
Grant 2013-4-29
编辑：Grant 2013-4-29
That works, thank you very much.
Would you mind giving a brief explanation as to why it does, as compared to what I was doing?
Thanks a lot.
EDIT: I just want to make sure, this will work if I give QAc a value right? or would I just remove QAc from the line "syms QAc f"?

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